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linux/arch/arm/kernel/entry-ftrace.S
Russell King 8478132a87 Revert "arm: move exports to definitions" 
This reverts commit 4dd1837d7589f468ed109556513f476e7a7f9121.

Moving the exports for assembly code into the assembly files breaks
KSYM trimming, but also breaks modversions.

While fixing the KSYM trimming is trivial, fixing modversions brings
us to a technically worse position that we had prior to the above
change:

- We end up with the prototype definitions divorsed from everything
  else, which means that adding or removing assembly level ksyms
  become more fragile:
  * if adding a new assembly ksyms export, a missed prototype in
    asm-prototypes.h results in a successful build if no module in
    the selected configuration makes use of the symbol.
  * when removing a ksyms export, asm-prototypes.h will get forgotten,
    with armksyms.c, you'll get a build error if you forget to touch
    the file.

- We end up with the same amount of include files and prototypes,
  they're just in a header file instead of a .c file with their
  exports.

As for lines of code, we don't get much of a size reduction:
 (original commit)
 47 files changed, 131 insertions(+), 208 deletions(-)
 (fix for ksyms trimming)
 7 files changed, 18 insertions(+), 5 deletions(-)
 (two fixes for modversions)
 1 file changed, 34 insertions(+)
 3 files changed, 7 insertions(+), 2 deletions(-)
which results in a net total of only 25 lines deleted.

As there does not seem to be much benefit from this change of approach,
revert the change.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
2016-11-23 10:00:03 +00:00

244 lines
5.3 KiB
ArmAsm
Raw Blame History

/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <asm/assembler.h>
#include <asm/ftrace.h>
#include <asm/unwind.h>
#include "entry-header.S"
/*
* When compiling with -pg, gcc inserts a call to the mcount routine at the
* start of every function. In mcount, apart from the function's address (in
* lr), we need to get hold of the function's caller's address.
*
* Older GCCs (pre-4.4) inserted a call to a routine called mcount like this:
*
* bl mcount
*
* These versions have the limitation that in order for the mcount routine to
* be able to determine the function's caller's address, an APCS-style frame
* pointer (which is set up with something like the code below) is required.
*
* mov ip, sp
* push {fp, ip, lr, pc}
* sub fp, ip, #4
*
* With EABI, these frame pointers are not available unless -mapcs-frame is
* specified, and if building as Thumb-2, not even then.
*
* Newer GCCs (4.4+) solve this problem by introducing a new version of mcount,
* with call sites like:
*
* push {lr}
* bl __gnu_mcount_nc
*
* With these compilers, frame pointers are not necessary.
*
* mcount can be thought of as a function called in the middle of a subroutine
* call. As such, it needs to be transparent for both the caller and the
* callee: the original lr needs to be restored when leaving mcount, and no
* registers should be clobbered. (In the __gnu_mcount_nc implementation, we
* clobber the ip register. This is OK because the ARM calling convention
* allows it to be clobbered in subroutines and doesn't use it to hold
* parameters.)
*
* When using dynamic ftrace, we patch out the mcount call by a "mov r0, r0"
* for the mcount case, and a "pop {lr}" for the __gnu_mcount_nc case (see
* arch/arm/kernel/ftrace.c).
*/
#ifndef CONFIG_OLD_MCOUNT
#if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 4))
#error Ftrace requires CONFIG_FRAME_POINTER=y with GCC older than 4.4.0.
#endif
#endif
.macro mcount_adjust_addr rd, rn
bic \rd, \rn, #1 @ clear the Thumb bit if present
sub \rd, \rd, #MCOUNT_INSN_SIZE
.endm
.macro __mcount suffix
mcount_enter
ldr r0, =ftrace_trace_function
ldr r2, [r0]
adr r0, .Lftrace_stub
cmp r0, r2
bne 1f
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ldr r1, =ftrace_graph_return
ldr r2, [r1]
cmp r0, r2
bne ftrace_graph_caller\suffix
ldr r1, =ftrace_graph_entry
ldr r2, [r1]
ldr r0, =ftrace_graph_entry_stub
cmp r0, r2
bne ftrace_graph_caller\suffix
#endif
mcount_exit
1: mcount_get_lr r1 @ lr of instrumented func
mcount_adjust_addr r0, lr @ instrumented function
badr lr, 2f
mov pc, r2
2: mcount_exit
.endm
.macro __ftrace_caller suffix
mcount_enter
mcount_get_lr r1 @ lr of instrumented func
mcount_adjust_addr r0, lr @ instrumented function
.globl ftrace_call\suffix
ftrace_call\suffix:
bl ftrace_stub
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
.globl ftrace_graph_call\suffix
ftrace_graph_call\suffix:
mov r0, r0
#endif
mcount_exit
.endm
.macro __ftrace_graph_caller
sub r0, fp, #4 @ &lr of instrumented routine (&parent)
#ifdef CONFIG_DYNAMIC_FTRACE
@ called from __ftrace_caller, saved in mcount_enter
ldr r1, [sp, #16] @ instrumented routine (func)
mcount_adjust_addr r1, r1
#else
@ called from __mcount, untouched in lr
mcount_adjust_addr r1, lr @ instrumented routine (func)
#endif
mov r2, fp @ frame pointer
bl prepare_ftrace_return
mcount_exit
.endm
#ifdef CONFIG_OLD_MCOUNT
/*
* mcount
*/
.macro mcount_enter
stmdb sp!, {r0-r3, lr}
.endm
.macro mcount_get_lr reg
ldr \reg, [fp, #-4]
.endm
.macro mcount_exit
ldr lr, [fp, #-4]
ldmia sp!, {r0-r3, pc}
.endm
ENTRY(mcount)
#ifdef CONFIG_DYNAMIC_FTRACE
stmdb sp!, {lr}
ldr lr, [fp, #-4]
ldmia sp!, {pc}
#else
__mcount _old
#endif
ENDPROC(mcount)
#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(ftrace_caller_old)
__ftrace_caller _old
ENDPROC(ftrace_caller_old)
#endif
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(ftrace_graph_caller_old)
__ftrace_graph_caller
ENDPROC(ftrace_graph_caller_old)
#endif
.purgem mcount_enter
.purgem mcount_get_lr
.purgem mcount_exit
#endif
/*
* __gnu_mcount_nc
*/
.macro mcount_enter
/*
* This pad compensates for the push {lr} at the call site. Note that we are
* unable to unwind through a function which does not otherwise save its lr.
*/
UNWIND(.pad #4)
stmdb sp!, {r0-r3, lr}
UNWIND(.save {r0-r3, lr})
.endm
.macro mcount_get_lr reg
ldr \reg, [sp, #20]
.endm
.macro mcount_exit
ldmia sp!, {r0-r3, ip, lr}
ret ip
.endm
ENTRY(__gnu_mcount_nc)
UNWIND(.fnstart)
#ifdef CONFIG_DYNAMIC_FTRACE
mov ip, lr
ldmia sp!, {lr}
ret ip
#else
__mcount
#endif
UNWIND(.fnend)
ENDPROC(__gnu_mcount_nc)
#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(ftrace_caller)
UNWIND(.fnstart)
__ftrace_caller
UNWIND(.fnend)
ENDPROC(ftrace_caller)
#endif
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(ftrace_graph_caller)
UNWIND(.fnstart)
__ftrace_graph_caller
UNWIND(.fnend)
ENDPROC(ftrace_graph_caller)
#endif
.purgem mcount_enter
.purgem mcount_get_lr
.purgem mcount_exit
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
.globl return_to_handler
return_to_handler:
stmdb sp!, {r0-r3}
mov r0, fp @ frame pointer
bl ftrace_return_to_handler
mov lr, r0 @ r0 has real ret addr
ldmia sp!, {r0-r3}
ret lr
#endif
ENTRY(ftrace_stub)
.Lftrace_stub:
ret lr
ENDPROC(ftrace_stub)
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